This invention generally relates to systems for monitoring exhaust gases produced by a vehicle engine and, in particular, such a system disabling the engine when a hazardous concentration of carbon monoxide is detected either inside or outside the vehicle.
Engines, such as those in automobiles, produce exhaust gases containing carbon monoxide as a result of incomplete combustion of carbon-based fuels. As is well known, carbon monoxide is a very poisonous gas. The presence of carbon monoxide in one's bloodstream reduces the level of oxygen in the blood, which in turn, starves the brain of oxygen. The lethal effect of carbon monoxide poisoning has been known since ancient times. Unfortunately, carbon monoxide is particularly dangerous because it is both colorless, tasteless and odorless making detection of the gas by human senses difficult.
Numerous carbon monoxide poisonings occur each year. Carbon monoxide poisoning results from voluntary or involuntary inhalation of exhaust gases in various situations including suicide, leaving an automobile running in a closed garage, idling the engine while being stranded in heavy snow drifts, and operating an automobile having a faulty exhaust system which discharges exhaust into the passenger compartment. Carbon monoxide poisoning deprives the brain of oxygen which can cause slight to severe incapacitation and even death. For example, the National Center for Health Statistics reports that, in 1988, 2,247 people committed suicide and 372 people died accidentally from inhalation of motor vehicle exhaust gases. Further, statistics from the National Safety Council's "Accident Facts" reveal that an average of 400 accidental deaths and 2300 suicide deaths occurred each year from 1986 to 1989 because of carbon monoxide poisoning.
Many systems are presently available for monitoring levels of carbon monoxide. However, present systems fail to solve several problems associated with detecting hazardous concentrations of carbon monoxide produced by a vehicle.
Present carbon monoxide monitoring and detection systems inform the vehicle operator of potentially dangerous levels of carbon monoxide. These systems, however, do not alleviate the problem by disabling the source of the noxious gas. Therefore, the risk of carbon monoxide poisoning continues after detection of the hazardous condition.
Disabling the source of carbon monoxide upon detection of a hazardous concentration of the gas may often cause false disablements. Often, the concentration of carbon monoxide is hazardous at a specific but short time and the carbon monoxide quickly dissipates. In these situations, disabling the source is unnecessary to the safety of the vehicle's passengers and is a nuisance to the vehicle operator. Also, being able to move the vehicle after one is aware of hazardous carbon monoxide levels can facilitate the dissipation of the gas.
Disabling a vehicle's engine upon detection of a hazardous level of carbon monoxide is also dangerous. Most vehicles lose steering control, braking power and the like when their engines stop running. This creates the risk of the operator losing control of the vehicle. In any event, moving vehicles are less likely to contain hazardous concentrations of the gas than stationary vehicles. Therefore, it is desirable to have a carbon monoxide detection system which will not disable operation of the engine when the vehicle is in motion.
Presently available carbon monoxide systems also lack a detector for detecting the concentration of carbon monoxide outside the vehicle. Such a detector, located outside the vehicle's passenger compartment, can aid in the prevention of "garage" deaths. In other words, when a person leaves the engine running inside a closed space, such as a garage, tile concentration of carbon monoxide reaches hazardous levels in the space surrounding tile vehicle. Advantageously, the source of the poisonous gas should be disabled when either the passenger compartment contains a dangerous level of carbon monoxide or when the air surrounding the vehicle contains a dangerous level.
Depending on the levels of carbon monoxide inside and outside the vehicle, it is often desirable to open or close the vehicle's windows to facilitate the dissipation of the hazardous gas. In particular, if tile concentration of carbon monoxide is greater inside the compartment than outside, opening the windows allows the harmful gas to escape. If the concentration of carbon monoxide is greater outside the compartment than inside, closing the windows helps prevent the gas from entering the compartment.